Mass sensing by detecting the quadrature of a coupled light field

Ultrasensitive detections have been proposed as an application of optomechanical systems. Here we develop an approach to mass sensing by comparing the detected quadratures of light field coupled to a mechanical resonator, whose slight change of the mass should be precisely measured. The change in the mass of the mechanical resonator will cause the detectable difference in the evolved quadrature of the light field, to which the mechanical oscillator is coupled. It is shown that the ultra-small change $\Delta m$ from a mass $m$ can be detected up to the ratio $\Delta m/m\sim 10^{-8}-10^{-7}$ by choosing the feasible system parameters.